Nothing magic, just put in there based on experience. You can find the story behind the original recommendation here
https://issues.apache.org/jira/browse/CASSANDRA-6487 Key reasoning for the desire comes from Patrick McFadden: "Yes that was in bytes. Just in my own experience, I don't recommend more than ~100 mutations per batch. Doing some quick math I came up with 5k as 100 x 50 byte mutations. Totally up for debate." It's totally changeable, however, it's there in no small part because so many people confuse the BATCH keyword as a performance optimization, this helps flag those cases of misuse. On Thu, Dec 11, 2014 at 2:43 PM, Mohammed Guller <moham...@glassbeam.com> wrote: > > Hi – > > The cassandra.yaml file has property called *batch_size_warn_threshold_in_kb. > * > > The default size is 5kb and according to the comments in the yaml file, it > is used to log WARN on any batch size exceeding this value in kilobytes. It > says caution should be taken on increasing the size of this threshold as it > can lead to node instability. > > > > Does anybody know the significance of this magic number 5kb? Why would a > higher number (say 10kb) lead to node instability? > > > > Mohammed > -- [image: datastax_logo.png] <http://www.datastax.com/> Ryan Svihla Solution Architect [image: twitter.png] <https://twitter.com/foundev> [image: linkedin.png] <http://www.linkedin.com/pub/ryan-svihla/12/621/727/> DataStax is the fastest, most scalable distributed database technology, delivering Apache Cassandra to the world’s most innovative enterprises. Datastax is built to be agile, always-on, and predictably scalable to any size. With more than 500 customers in 45 countries, DataStax is the database technology and transactional backbone of choice for the worlds most innovative companies such as Netflix, Adobe, Intuit, and eBay.
